The alternator load imposed on an engine can be adjusted based on driver demanded engine torque in order to improve fuel economy. For example, alternator load may be decreased with increasing engine torque demands, and may be increased with decreasing engine torque demands. Furthermore, fuel economy can be improved by scheduling alternator charging preferentially during vehicle deceleration to capture energy via regenerative braking, and by turning off the alternator charging at wide-open throttle to improve vehicle acceleration.
However, the inventors herein have recognized various issues with the above approach. Namely, the above conventional alternator control strategies fail to recognize the fuel efficiency penalty (e.g. marginal fuel cost) for converting fuel to shaft work while charging the battery with the alternator during engine operating conditions where marginal fuel cost is higher such as spark retard, fuel enrichment, high engine speeds, and when the engine is operating near a transmission downshift threshold. Accordingly, during these engine operating conditions, following conventional alternator control strategies may unnecessarily cause increases in fuel consumption.
In one example, the issues described above may be at least partially addressed by a method comprising: in response to a state of charge (SOC) of a vehicle battery increasing above a threshold SOC, reducing an alternator charging based on one or more of a spark timing, an engine speed, an air-fuel ratio, and an engine load.
In another example, a method for an engine may comprise: adjusting an alternator torque in response to a state of charge (SOC) of a vehicle battery increasing above a threshold SOC, the adjusting based on one or more of a spark timing, an engine speed, an air-fuel ratio, and an engine load.
In another example, a vehicle system may comprise: an engine; an alternator mechanically coupled to the engine and electrically coupled to a battery; a controller on-board the engine, including executable instructions to, in response to a battery state of charge (SOC) being greater than a threshold SOC, adjusting an alternator torque based on one or more of a spark timing, an air-fuel ratio, an engine speed, and an engine load.
In this way, the technical result of reducing fuel consumption while maintaining a battery SOC for operation of front-end accessories may be achieved. Furthermore, fuel consumption and exhaust emissions may be reduced during aggressive vehicle driving conditions such has high engine loads near transmission downshift thresholds and high engine speeds. For example, avoidance of alternator charging at high loads will reduce engine load and spark retard, which may reduce the need for high load enrichment and thus reduce hydrocarbon and carbon monoxide emissions.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.